PICRITE SILLS AND CRYSTAL-MELT REACTIONS IN THE HONNINGSVAG INTRUSIVESUITE, NORTHERN NORWAY

Field relations in the upper part of Intrusion II of the Caledonian Ho nningsvag Intrusive Suite show that some peridotite sheets transgress, and include in situ rafts of, the adjacent gabbroic cumulates. Modal and textural analyses of three olivine melagabbro sheets show non-cote ctic mineral proportions that are likely to result from crystal-melt r eactions. Discordant, replacive fingers and pipes of feldspathic perid otite along interfaces between peridotite and overlying olivine melaga bbro also suggest crystal-melt reactions. It is proposed that several picritic sills intruded porous gabbroic cumulates in the upper part of Intrusion II. Lateral infiltration of picritic magma led to crystal-m elt reactions, mainly assimilation of plagioclase and precipitation of olivine, resulting in the formation of olivine melagabbro and peridot ite sheets, and replacive fingers and pipes of feldspathic peridotite.